Drilling techniques
Drilling preparation. When drilling a hole with a length of more than two diameters of the drill, it is recommended that the hole is first rigidly fixed in the quill short.Then the subsequent drill will be better guided and will be led away less.
Drill feed. The drill is fed by rotating the tailstock handwheel.
When drilling a deep hole with a twist drill, it is necessary from time to time to remove the drill from the hole while the machine is running and remove it from the shavings; this prevents breakage of the drill. It is also necessary to ensure that when drilling with normal drills, the hole depth does not exceed the length of the spiral flute of the drill, otherwise the chips will not be able to come out of the flutes and the drill will break.
Blind hole drilling. To drill holes of a given length, it is convenient to use the risks from the tailstock quill (see Fig. 165). By rotating the drill, the drill is pushed out until it goes deep into the material with the entire intake part, and at the same time notice the corresponding risk on the quill. Then, rotating the tailstock handwheel, move the quill until it comes out of the body by the required number of divisions.
When there are no divisions on the quill, the following method can be applied. Mark the required hole length on the drill with chalk and move the quill until the drill goes deep into the marks.
Sometimes, when drilling, a characteristic metallic squeal is heard. This is a sign of a skewed hole or a blunt drill. In such cases, you must immediately stop the feed, stop the machine, find out and eliminate the cause of the squeal.
Before stopping the machine during drilling, the drill must be pulled out of the hole. It is impossible to stop the machine while the drill is in the hole, this can lead to jamming of the drill and its breakage.
Drilling feed. Cutting forces, torque and power when drilling
Work on drilling holes in metal, depending on the type of holes and the properties of the metal, can be performed with different tools and using different techniques. We would like to tell you about drilling methods, tools, as well as safety precautions when performing these works.
Drilling holes in metal may be needed when repairing engineering systems, household appliances, a car, creating structures from sheet and profile steel, designing crafts from aluminum and copper, making boards for radio equipment, and in many other cases. It is important to understand what tool is needed for each type of work, so that the holes are of the right diameter and in a strictly designated place, and what safety measures will help to avoid injuries.
Holemaking
Types of holes in metal and how to drill them
- deaf;
- end-to-end;
- half (incomplete);
- deep;
- large diameter;
- for internal thread.
Thread holes require the definition of diameters with tolerances set in GOST 16093-2004. For common hardware, the calculation is shown in table 5.
Table 5. Ratio of metric and inch threads, as well as selection of hole size for pre-drilling
| Metric thread | Inch thread | Pipe thread | |||||||
| Thread diameter | Thread pitch, mm | Thread hole diameter | Thread diameter | Thread pitch, mm | Thread hole diameter | Thread diameter | Thread hole diameter | ||
| min. | Max. | min. | Max. | ||||||
| M1 | 0.25 | 0.75 | 0.8 | 3/16 | 1,058 | 3.6 | 3.7 | 1/8 | 8.8 |
| M1.4 | 0.3 | 1.1 | 1.15 | 1/4 | 1,270 | 5.0 | 5.1 | 1/4 | 11.7 |
| M1.7 | 0.35 | 1,3 | 1.4 | 5/16 | 1.411 | 6.4 | 6.5 | 3/8 | 15.2 |
| M2 | 0,4 | 1.5 | 1.6 | 3/8 | 1.588 | 7,7 | 7.9 | 1/2 | 18.6 |
| M2.6 | 0,4 | 2.1 | 2.2 | 7/16 | 1,814 | 9.1 | 9.25 | 3/4 | 24.3 |
| M3 | 0.5 | 2.4 | 2.5 | 1/2 | 2.117 | 10.25 | 10.5 | one | 30.5 |
| M3.5 | 0.6 | 2.8 | 2.9 | 9/16 | 2.117 | 11.75 | 12.0 | – | – |
| М4 | 0.7 | 3.2 | 3.4 | 5/8 | 2.309 | 13.25 | 13.5 | 11/4 | 39.2 |
| M5 | 0.8 | 4.1 | 4.2 | 3/4 | 2,540 | 16.25 | 16.5 | 13/8 | 41.6 |
| M6 | 1.0 | 4.8 | 5.0 | 7/8 | 2.822 | 19.00 | 19.25 | 11/2 | 45.1 |
| М8 | 1.25 | 6.5 | 6,7 | one | 3.175 | 21.75 | 22.0 | – | – |
| M10 | 1.5 | 8.2 | 8.4 | 11/8 | 3.629 | 24.5 | 24.75 | – | – |
| M12 | 1.75 | 9.9 | 10.0 | 11/4 | 3.629 | 27.5 | 27.75 | – | – |
| M14 | 2.0 | 11.5 | 11.75 | 13/8 | 4.233 | 30.5 | 30.5 | – | – |
| М16 | 2.0 | 13.5 | 13.75 | – | – | – | – | – | – |
| M18 | 2.5 | 15.0 | 15.25 | 11/2 | 4.333 | 33.0 | 33.5 | – | – |
| M20 | 2.5 | 17.0 | 17.25 | 15/8 | 6,080 | 35.0 | 35.5 | – | – |
| M22 | 2.6 | 19.0 | 19.25 | 13/4 | 5.080 | 33.5 | 39.0 | – | – |
| M24 | 3.0 | 20.5 | 20.75 | 17/8 | 5.644 | 41.0 | 41.5 | – | – |
Complex holes
Holes located on the edge of the workpiece (half) can be made by connecting two workpieces or the workpiece and the gasket with the edges and clamping them with a vice and drilling a full hole. The gasket must be made of the same material as the workpiece to be machined, otherwise the drill will “go” towards the least resistance.
A through hole in the corner (shaped metal rolling) is performed by fixing the workpiece in a vice and using a wooden gasket.
It is more difficult to drill a cylindrical workpiece tangentially. The process is divided into two operations: preparation of the platform perpendicular to the hole (milling, countersinking) and the actual drilling. Drilling holes in angled surfaces also begins with site preparation, after which a wooden spacer is inserted between the planes, forming a triangle, and a hole is drilled through the corner.
Hollow parts are drilled by filling the cavity with wood cork.
Shoulder holes are produced using two techniques:
- Reaming. The hole is drilled to the full depth with a drill of the smallest diameter, after which it is reamed to a given depth with drills with diameters from smaller to larger. The advantage of the method is a well-centered hole.
- Reducing the diameter. A hole of the maximum diameter is drilled to a given depth, then the drills are changed with a sequential decrease in the diameter and deepening of the hole. This method makes it easier to control the depth of each step.
Reaming the hole. 2. Reducing the diameter
Drill
Drilling shallow holes is performed with pen and twist drills.
Perforated drill. A pen drill is shown in fig. 159. The cutting part of the drill is a flat blade 3, turning into a rod 4. The two cutting edges 1 and 2 of the drill are inclined to each other usually at an angle of 116-118 °, but this angle can be from 90 to 140 °, depending on the hardness processed material: the harder the material, the greater the angle.
Pen drills are ineffective, in addition, when drilling, they are pulled away from the axis of the hole. Despite this, they are sometimes used for irresponsible work, which is explained by the simplicity of the design of such drills and their low cost.
Twist drills. Currently, drilling is performed mainly with twist drills. In fig. 160 shows such a drill. It consists of working part and shank (conical according to Fig. 160, a or cylindrical according to Fig. 160, b) for fastening the drill either in the tapered hole of the tailstock quill, or in the chuck.
The tapered shank has foot. which serves as an emphasis when knocking out a drill (Fig. 160, a).
The working part of the twist drill is a cylinder with two spiral (or rather, helical) grooves, which serve to form the cutting edges of the drill and remove the chips outside. The front part of the drill (Fig. 160, c) is sharpened along two conical surfaces and has rake face, rake face, two cutting edges. connected jumper (transverse edge). Two narrow ribbons (chamfers) along the helical grooves of the drill serve for correct direction and centering of the drill.
The 2φ drill point is usually 116.118 °. For drilling in hard materials, this angle is increased to 140 °, and for drilling in soft materials it is reduced to 90 °.
Drills are made of alloy steel 9XC, high-speed steel P9 and P18, as well as alloy steel with soldered carbide plates.
Drills equipped with carbide plates are shown in fig. 161. Drills with straight flutes (Fig. 161, a) are easier to manufacture, but the exit of chips from the hole is difficult; they are usually used when drilling cast iron and other brittle metals, when the hole depth does not exceed two to three diameters. Drills with helical flutes (Fig. 161, b) more easily remove the chips from the hole, so they are recommended for use when drilling viscous materials.
Anchoring drills
The way of fixing the drill depends on the shape of its shank. Drill with cylindrical shank fixed in the tailstock quill by means of special cartridges; drills with taper shank they are fixed directly in the tapered hole of the tailstock pintles. Taper shanks in tools, as well as tapered holes in the spindles and pins of lathes, are made according to the Morse system. Morse cones are numbered 0, 1, 2, 3, 4, 5, 6; each number corresponds to a certain size. If the taper of the drill is less than the tapered hole of the tailstock quill, then put on the drill shank 1 adapter sleeve 2 and then the sleeve together with the drill is inserted into the hole of the tailstock quill of the machine.
Before inserting the drill into the tailstock quill, it is necessary to thoroughly clean the drill shank from dirt, as well as the quill hole.
To remove the drill from the tailstock quill, turn the handwheel until the quill is pulled into the tailstock housing to the end position. In this position, the screw will rest against the end of the shank and push it out.
Tools, fixtures, drills
The main drilling tools are hand and power drills and, if possible, drilling machines. The working body of these mechanisms. a drill. can have a different shape.
- spiral (most common);
- screw;
- crowns;
- conical;
- feathers, etc.
The production of drills of various designs is standardized by numerous GOSTs. Drills up to Ø 2 mm are not marked, up to Ø 3 mm. the shank indicates the section and steel grade, larger diameters may contain additional information. To obtain a hole of a certain diameter, you need to take a drill a few tenths of a millimeter smaller. The better the drill is sharpened, the smaller the difference between these diameters.
Drills differ not only in diameter, but also in length. they are produced short, elongated and long. The limiting hardness of the processed metal is also important information. The drill shank can be cylindrical or tapered, which should be borne in mind when choosing a drill chuck or adapter sleeve.
Drill with cylindrical shank. 2. Drill with a tapered shank. 3. Drill with a sword for carving. 4. Center drill. 5. Drill with two diameters. 6. Center drill. 7. Conical drill. 8. Conical multistage drill
Some work and materials require special sharpening. The harder the metal being processed, the sharper the edge should be. For thin sheet metal, a conventional twist drill may not work; you will need a tool with a special sharpening. Detailed recommendations for various types of drills and workable metals (thickness, hardness, hole type) are quite extensive, and we will not consider them in this article.
Various types of drill sharpening. 1. For rigid steel. 2. For stainless steel. 3. For copper and copper alloys. 4. For aluminum and aluminum alloys. 5. For cast iron. 6. Bakelite
Standard sharpening. 2. Free sharpening. 3. Diluted sharpening. 4. Heavy sharpening. 5. Separate sharpening
To fix parts before drilling, vices, stops, conductors, corners, clamps with bolts and other devices are used. This is not only a safety requirement, but in fact it is more convenient, and the holes are of better quality.
For chamfering and processing the surface of the channel, use a countersink of a cylindrical or conical shape, and for marking a point for drilling and so that the drill does not “jump off”. a hammer and a center punch.
Deep holes, coolant
Sometimes a deep hole is required. In theory, this is a hole that is five times its diameter. In practice, deep drilling is called drilling, requiring periodic forced removal of chips and the use of coolants (cutting fluids).
In drilling, coolant is needed primarily to reduce the temperature of the drill and workpiece, which are heated by friction. Therefore, when making holes in copper, which has a high thermal conductivity and is itself capable of removing heat, the coolant can be omitted. Cast iron can be drilled relatively easily and without lubrication (except for high-strength).
11 DRILLING TIPS AND TRICKS (And Mistakes To Avoid!)
In production, industrial oils, synthetic emulsions, emulsols and some hydrocarbons are used as coolants. In home workshops, you can use:
- technical petroleum jelly, castor oil. for mild steels;
- laundry soap. for aluminum alloys such as D16T;
- a mixture of kerosene with castor oil. for duralumin;
- soapy water. for aluminum;
- turpentine diluted with alcohol. for silumin.
Cutting Speed | Machining Operations | Manufacturing Processes
The universal refrigerated liquid can be prepared independently. To do this, you need to dissolve 200 g of soap in a bucket of water, add 5 tablespoons of engine oil, you can waste it, and boil the solution until a soapy homogeneous emulsion is obtained. Some craftsmen use lard to reduce friction.
| Processed material | Coolant lubricant |
| Steel: | |
| carbonaceous | Emulsion. Sulfurized oil |
| structural | Sulfurized kerosene oil |
| instrumental | Mixed oils |
| alloyed | Mixed oils |
| Malleable cast iron | 3-5% emulsion |
| Iron casting | No refrigeration. 3-5% emulsion. Kerosene |
| Bronze | No refrigeration. Mixed oils |
| Zinc | Emulsion |
| Brass | No refrigeration. 3-5% emulsion |
| Copper | Emulsion. Mixed oils |
| Nickel | Emulsion |
| Aluminum and its alloys | No refrigeration. Emulsion. Mixed oils. Kerosene |
| Stainless, heat-resistant alloys | A mixture of 50% sulfurized oil, 30% kerosene, 20% oleic acid (or 80% sulfofresol and 20% oleic acid) |
| Fiber, vinyl plastic, plexiglass and so on | 3-5% emulsion |
| Textolite, getinax | Compressed air blowing |
Deep holes can be made with solid and circular drilling, and in the latter case, the central rod formed by the rotation of the crown is not broken out entirely, but in parts, weakening it with additional small-diameter holes.
Solid drilling is performed in a well-fixed workpiece with a twist drill, into the channels of which coolant is supplied. Periodically, without stopping the rotation of the drill, you need to remove it and clean the cavity from chips. Work with a twist drill is performed in stages: first, take a short one and drill a hole, which is then buried with a drill of the appropriate size. With a significant hole depth, it is advisable to use guide bushings.
If you regularly drill deep holes, you can recommend purchasing a special machine with automatic coolant supply to the drill and accurate centering.
Cutting conditions when drilling with twist drills Spindle speed rpm Feed per revolution mm / rev Work material Steel Aluminum Stainless steel Titanium Ebonite
19 Catalog NORGAU 2015 Cutting measuring tools for locksmith Accessories Page 3
Cutting conditions when drilling with twist drills Spindle speed rpm Feed per revolution mm / rev Work material Steel Aluminum Stainless steel Titanium Ebonite
Cutting conditions when drilling with twist drills Spindle speed rpm Feed per revolution mm / rev Work material Steel Aluminum Stainless steel Titanium Hardwood _ Drills Point angle Cooling Cutting speed Drill diameter 2 5 8 12 16 25 40 63 80 Automatic steels 500 N / mm2 HSS 118 Emulsion 30-50 5600 005 2250 012 1400 020 930 025 700 030 450 040 280 040 180 050 160 050 alloyed structural steels 500 N / mm2 HSS 118 Emulsion 30-40 5600 005 2250 012 1400 020 930 025 700 030 450 040 280 040 180 050 140 060 0. Unalloyed structural steels 500-700 N / mm2 Emulsion 4750 1900 1200 800 600 400 240 150 120 005 012 020 025 030 035 040 050 060 Unalloyed structural steels 700-900 N / mm2 Emulsion 2100 003 860 007 540 010 360 270 170 110 68 50 016 020 025 032 040 050 Unalloyed structural steels 700 N / mm2 Emulsion 3980 003 1580 007 995 010 665 016 495 020 320 025 200 032 125 040 100 050 Alloyed steels Alloyed steels 700-900 N / mm2 Alloyed steels (Cr-Ni) 900-1100 N / mm2 Alloy steels (Cr-Ni-Mo) 1100-1400 N / mm2 Stainless steels Heat-resistant steels Manganese steels 10% Mp Spring steels Nimonic Hastelloy Inconnel HSS HSS-E HSS-E HSS-E HSS-E 118 130 130 130 Emulsion oil Emulsion Emulsion oil Emulsion oil Emulsion oil Emulsion oil Dry processing (preheated workpiece 200-300 Emulsion oil 5-10 3-8 2380 002 2100 002 1590 002 1275 002 1275 002 1275 002 1590 002 875 002 950 005 860 005 635 005 505 005 505 005 505 005 635 005 350 005 595 008 540 008 400 008 320 008 320 008 320 008 400 012 360 012 265 012 210 012 210 012 210 012 300 014 270 014 200 014 160 014 160 014 160 014 190 018 170 018 125 018 100 018 100 018 100 018 120 023 110 023 80 023 65 023 65 023 400 008 220 008 265 012 145 012 200 014 110 014 125 018 80 023 Aluminum alloys (long-chipped) Aluminum alloys (short-chipped) Sitlumine alloys Magnesium alloys Zinc alloys Hard plastics (thermosets) Soft plastics (thermoplastics ) Plexiglass Ebonite HSS HSS HSS HSS HSS HSS HSS 130 130 118 (130) 130 (118) 118 (130) 130 80 80 Emulsion Emulsion Emulsion Emulsion Dry processing Emulsion Compressed air Compressed air Water Compressed air 40-100 30-65 30-60 11140 005 7600 005 7200 005 6365 005 4435 014 3030 014 2900 014 2535 008 12740 5100 008 018 10-20 20-40 15-25 15-35 6800 005 2380 005 4745 005 3185 005 3980 008 2700 014 950 014 1900 014 1265 014 1585 018 2785 018 1900 018 1800 018 1590 014 3200 025 1700 018 595 018 1195 018 795 018 995 025 1855 022 1260 022 1200 022 1060 020 2100 030 1130 020 400 020 795 020 530 020 665 030 1395 030 950 030 900 030 795 025 1600 035 850 025 300 025 595 025 400 025 495 035 890 040 600 040 580 040 510 030 1020 040 540 030 190 030 380 030 255 030 320 040 027 68 027 50 027 40 027 40 027 50 027 25 027 555 045 380 045 360 045 320 040 640 050 340 040 120 040 240 040 160 040 200 050 032 50 032 40 032 023 027 032 32 032 32 032 635 255 160 105 80 50 30 20 16 002 005 008 012 014 018 023 027 03 2 40 032 350 050 240 050 230 050 200 050 400 060 215 050 750 050 150 050 100 050 125 060 280 060 190 060 180 060 160 060 320 070 170 060 120 060 100 070 NORGAU 3
Drilling cutting conditions when drilling holes
The main elements of the cutting mode when drilling are cutting speed, feed and depth of cut. Cutting speed is the peripheral speed of the point of the cutting edge farthest from the center of the drill, measured in meters per minute (m / min).
Cutting Speeds for Drilling (Cooling Operation) Structural Steels
Cutting speed v is determined by the formula
Where D. drill diameter; n. the number of revolutions of the spindle in min.; π = 3.14 is a constant number. The number of revolutions of the cutting tool is determined by the formula
When drilling or reaming holes, it is important to select the correct cutting speed at which the tool will perform normally, i.e., most efficiently. Thus, the cutting speed of the cutting tool and its feed per revolution constitute the cutting mode. The cutting mode must be selected so as to keep the tool from premature wear while taking into account maximum productivity. Cutting data can be selected according to table. 19 and 20. Table 20
Conversion table for cutting speeds and drill revolutions per minute
Knowing the diameter of the drill and the material of the workpiece, we find from the table. 19 and 20, the cutting speed, and according to the cutting speed and the diameter of the drill, we determine the number of revolutions of the drill per minute according to the conversion table (or according to the formula). The found speed and feed value are compared with the actual speed of the machine spindle. Each machine has a table of spindle revolutions and feeds, which is attached to the machine. When working with drills made of carbon steel, the values of cutting speed and feed should be reduced by 30. 40%. To reduce friction and heating the tool during drilling, a coolant is used. With a generous use of coolant when drilling steel, the cutting speed can be increased by about 30. 35%. In addition, ample cooling makes it easier to remove chips from the hole. For normal cooling, it is necessary to feed at least 10 l coolant per minute. When drilling various metals and alloys, it is recommended to use the coolants given in table. 21.
Recommended coolants for various metals and alloys
Structural and tool steel
Soap emulsion or a mixture of mineral and fatty oils (castor, rapeseed)
Kerosene with castor or rapeseed oil. Soap emulsion
Soap emulsion or mixture of alcohol and turpentine
If the cutting edge of the drill becomes dull quickly during operation, this is a sign that the cutting speed is too high and must be reduced. When chipping cutting edges, reduce the feed rate. To prevent bluntness and breakage of the drill at the exit from the hole, it is recommended to reduce the feed at the moment of the drill exit. To obtain holes of a high class of accuracy, the reamers in the machine spindle are mounted on special swinging mandrels, which enable the reamer to take the required position in the hole. This eliminates the “breaking” of the hole. To obtain high purity of hole processing during operation, the reamer should be lubricated with vegetable oil. The cutting speed when reaming holes in steel is taken to be from 5 to 10 m / min, feed. from 0.3 to 1.3 mm / rev. Table 22 shows the values \ u200b \ u200bof cutting speed when reaming holes in various metals.
Average cutting speeds with reamers on drilling machines in m / min
The number of revolutions when drilling various types of metal
| Unalloyed steel | 4780 | 1910 | 960 | 640 | 480 | 26-30 |
| Sheet steel | 4480 | 1780 | 890 | 590 | 440 | 26-28 |
| Unalloyed tool steel | 4460 | 1780 | 890 | 590 | 440 | 26-28 |
| Alloy tool steel | 3980 | 1600 | 800 | 530 | 400 | 12-14 |
| Stainless steel | 2390 | 960 | 480 | 320 | 240 | 14-16 |
| Spring steel | 1450 | 570 | 290 | 190 | 140 | 8-10 |
| Gray cast iron | 4460 | 1780 | 890 | 590 | 450 | 25-30 |
| Malleable cast iron | 4460 | 1780 | 890 | 590 | 450 | 25-30 |
| Steel casting | 3500 | 1400 | 700 | 460 | 350 | 20-24 |
| Alloy aluminum | 7950 | 3180 | 590 | 1060 | 790 | 50-60 |
| Alloy copper | 4780 | 1910 | 960 | 640 | 480 | 28-30 |
| Bronze | 7960 | 3180 | 1500 | 1060 | 790 | 40-60 |
| Brass | 7960 | 3180 | 1500 | 1080 | 790 | 40-60 |
Recommended cooling when drilling any material. drilling emulsion or cooling oil, except for drilling in cast iron and bronze. where drilling must be done dry.
TIN coated drills. for increased loads in industrial production and in the workshop. Titanium nitride coating reduces drilling friction and thus increases productivity.
Cobalt drills HSS Co (Р6М5К5). high precision steel expert. Alloying with cobalt provides heat resistance and, at the same time, high wear resistance. The ideal solution for high precision drilling in corrosive applications. and heat-resistant steels with tensile strength up to 1000 N / mm2.
Cooling is recommended in any case when drilling in metal. But since the implementation of this recommendation is not always possible, twist drills are designed in such a way that the optimal result is achieved through rapid chip evacuation.